SUMMARY

If I set automatic discover of proxy configuration, all work fine. The problem comes out if I restart my system without changing back that proxy configuration:

- wifi network connection in network manager won't work anymore. If I try to connect to a wireless network it tries for a minute and then returns back to a disconnected state. After a minute an error message comes out from kde notifications saying "No agents were available for this request".


If I try to change password for connection, that password is not saved in networkmanager (if I open connection configuration there is a blank password, and if I try to connect it asks for password again and again). 
- Some program like thunderbird wont show up (it starts but is not shown, seems to be somehow frozen).
Finally, if I try to set back proxy configuration to "no proxy" after previous reboot, the configuration windows freezes for 10 seconds and then asks for a reboot to apply new configuration (never heppended before last kde upgrade) 

STEPS TO REPRODUCE
1. Set proxy configuration to "Automatically discover proxy settings"
2. Reboot
3. Try to connect to a wifi network

OBSERVED RESULT
It cannot connect to wifi

EXPECTED RESULT


SOFTWARE/OS VERSIONS

Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.17.2
KDE Frameworks Version: 5.63.0
Qt Version: 5.13.1